The present invention relates generally to a method and a system for effectively manufacturing fine-grained solid-state silicon monoxide (SiO). More specifically, the invention relates to a method for producing fine SiO of grain size less than or equal to 1 .mu.m in the amorphous form at substantially high yield, and further relates to a system for effectively implementing the process of the invention. In particular, the invention relates to a method and system for producing an industrially suitable fine SiO.
Fine-grained SiO powder is known as a very attractive material in the fine ceramic industries. For example, such fine-grained SiO is known as a material for making Si.sub.3 N.sub.4, SiC and so forth. Substantially fine-grained SiO, such as that having a grain size of less than or equal to 1 .mu.m is substantially active and thus useful as a material for ceramics.
Japanese Patent Second (examined) Publication (Tokko) Showa 59-50601 discloses the production of a fine-grained SiO powder. In the disclosed process, a mixture of silicon dioxide (SiO.sub.2) and carbon (C) or SiO.sub.2 and metallic silicon (Si) is heated at a temperature higher than or equal to 1500.degree. C. under reduced pressure to cause a thermal reaction for generating SiO vapor. The SiO vapor generated is condensed into a fine-grained solid-state SiO powder having a grain size of 1 .mu.m in amorphous form by causing adiabatic expansion in a nitriding or carbonizing reduction atmosphere or a pressure-reduced oxygen atmosphere.
Such a conventional production process for SiO is suitable for producing a small amount of fine SiO powder. However, when a large amount of SiO powder has to be produced, the conventional process and system encounter difficulties. For example, condensation of vapor-state SiO tends to be caused in the transporting duct or pipe for transporting the SiO vapor to the chamber in which adiabatic expansion is taking place. Condensation of SiO in the transporting duct causes accumulation of solid-state SiO in the duct, resulting in a blocked duct. Furthermore, the nozzle for discharging SiO vapor into the adiabatic expansion chamber is vulnerable to corrosion by SiO vapor and tends to be blocked by solid-state SiO condensed and accumulated in the nozzle.
Therefore, the process and system proposed in the aforementioned Japanese Patent Publication is considered as one for laboratory use and is, indeed, not applicable for industrial application.
Although SiO has been known as one important material in the ceramics industries, there has heretofore been no way of manufacturing large amounts of fine-grained SiO powder.